Abstract
In the present numerical study, implicit large eddy simulations (LES) of non-reacting multi-components mixing processes of cryogenic nitrogen and n-dodecane fuel injections under transcritical and supercritical conditions are carried out, using a modified reacting flow solver, originally available in the open source software OpenFOAM®. To this end, the Peng-Robinson (PR) cubic equation of state (EOS) is considered and the solver is modified to account for the real-fluid thermodynamics. At high pressure conditions, the variable transport properties such as dynamic viscosity and thermal conductivity are accurately computed using the Chung transport model. To deal with the multicomponent species mixing, molar averaged homogeneous classical mixing rules are used. For the velocity-pressure coupling, a PIMPLE based compressible algorithm is employed. For both cryogenic and non-cryogenic fuel injections, qualitative and quantitative analyses are performed, and the results show significant effects of the chamber pressure on the mixing processes and entrainment rates. The capability of the proposed numerical model to handle multicomponent species mixing with real-fluid thermophysical properties is demonstrated, in both supercritical and transcritical regimes.
Highlights
Fuel injections in cryogenic rockets, high-pressure diesel engines, or gas-turbines, operating at transcritical and supercritical conditions, have gained a significant interest following the perspective of emission reduction and improvement of engine efficiency
The turbulent jet mixing processes regarding cryogenic liquid nitrogen (L-N2 ) and n-dodecane injected into a quiescent gaseous nitrogen (G-N2 ) environment are examined, under transcritical and supercritical conditions, for various chamber pressures and injection temperatures
The injected fluid at sub/trans critical temperature into supercritical condition of the chamber typically heats up beyond its critical temperature as it mixes with the surrounding hot gas before it burns inside the combustion chamber and this process is referred to as “transcritical”
Summary
Fuel injections in cryogenic rockets, high-pressure diesel engines, or gas-turbines, operating at transcritical and supercritical conditions, have gained a significant interest following the perspective of emission reduction and improvement of engine efficiency In these applications, fuel injections in high-pressure and high-temperature conditions have recently been considered as a way to enhance the engine thermal efficiency and the power output, with reduced soot and NOx emissions [1]. Fuel injections in high-pressure and high-temperature conditions have recently been considered as a way to enhance the engine thermal efficiency and the power output, with reduced soot and NOx emissions [1] These elevated pressure conditions translate to chambers operating at pressures and temperatures exceeding fuel critical values. The jet disintegration behavior occurring under transcritical and supercritical conditions deviates from the subcritical conditions where the formation of liquid ligaments and droplets are replaced by turbulent gas jet mixing processes with widening of the diffusion layer of the liquid-gas interface [4,5]
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